Dometic Fridge Problem

Hi guys,
We've been using our van almost every weekend, normally wilding off grid with no problems.
We were on our way to Cardiff on Saturday (to a site, thankfully) when there was a buzzing noise coming from the rear. I got up to see and the noise was coming from the fridge. I turned it off and checked the control panel which showed both battery as flat! No figures at all showing.
We got to campsite plugged into hook-up and the fridge was working fine.
As we were leaving started the engine tried it again on 12v and watched as it drained the battery again.
Any solutions gratefully received.
Jill

It could be that with time you've got a loose connection somewhere on the 12v system. On 12v the fridge should run via a relay from the van battery, not the habitation battery (my understanding anyway). Have you checked the fuses? You may have to contact Dometic to send out an engineer. (I asked it's age 'cos Dometic fridges have a 3 year warranty) or take it back to your dealer if you bought it from a dealer.

Thanks.
We haven't had chance to check anything yet. I was hoping for some pointers to save a little time starting from scratch. Hubby is a mechanic and we have a garage but electrics aren't his strong point lol.